static Map<TokenAndRange, S> ai_matchTwoTokenizations(LS l1, LS l2) {
  int n = l(l1);
  if (n != l(l2)) null;
  L<TokenAndRange> l1t = addRangesToTokenization(l1);
  new LinkedHashMap<TokenAndRange, S> map;
  for i to n: {
    TokenAndRange a = l1t.get(i);
    S b = l2.get(i);
    if (!eqic(a.token, b))
      map.put(a, b);
  }
  ret map;
}